feat: 实现文件浏览器功能

- 添加 /api/files 路由支持目录浏览和文件读取
- 支持 list、read、stat、tree 四个端点
- 安全路径检查防止目录遍历攻击
- 创建 FileBrowser React 组件
- 支持目录导航、文件预览、隐藏文件切换
- 在 Web UI 中添加可切换的文件浏览面板

packages/web/src/api/client.ts

@@ -94,3 +94,70 @@ export function createWebSocket(sessionId: string): WebSocket {
   const host = window.location.host;
   return new WebSocket(`${protocol}//${host}/api/ws/${sessionId}`);
 }
+
+// Files
+export interface FileInfo {
+  name: string;
+  path: string;
+  type: 'file' | 'directory';
+  size: number;
+  modified: string;
+  extension?: string;
+}
+
+export interface FileListResponse {
+  success: boolean;
+  data: {
+    path: string;
+    absolutePath: string;
+    parent: string | null;
+    files: FileInfo[];
+  };
+}
+
+export interface FileReadResponse {
+  success: boolean;
+  data: {
+    path: string;
+    name: string;
+    type: string;
+    size: number;
+    modified: string;
+    content: string;
+    encoding: 'utf-8' | 'base64';
+  };
+}
+
+export interface FileTreeNode {
+  name: string;
+  path: string;
+  type: 'file' | 'directory';
+  children?: FileTreeNode[];
+}
+
+export interface FileTreeResponse {
+  success: boolean;
+  data: {
+    path: string;
+    tree: FileTreeNode[];
+  };
+}
+
+export async function getWorkingDirectory(): Promise<{ success: boolean; data: { workingDirectory: string; separator: string } }> {
+  return request('GET', '/files');
+}
+
+export async function listFiles(path: string = '.', showHidden: boolean = false): Promise<FileListResponse> {
+  const params = new URLSearchParams({ path });
+  if (showHidden) params.set('hidden', 'true');
+  return request('GET', `/files/list?${params}`);
+}
+
+export async function readFile(path: string): Promise<FileReadResponse> {
+  return request('GET', `/files/read?path=${encodeURIComponent(path)}`);
+}
+
+export async function getFileTree(path: string = '.', depth: number = 3): Promise<FileTreeResponse> {
+  const params = new URLSearchParams({ path, depth: String(depth) });
+  return request('GET', `/files/tree?${params}`);
+}